Hum Reprod. 2014 Jul;29(7):1471-89. doi: 10.1093/humrep/deu117. Epub 2014 May 20.
How does maternal cigarette smoking disturb development of the human fetal ovary?
Maternal smoking increases fetal estrogen titres and dysregulates several developmental processes in the fetal ovary.
Exposure to maternal cigarette smoking during gestation reduces human fetal ovarian cell numbers, germ cell proliferation and subsequent adult fecundity.
STUDY DESIGN, SIZE, DURATION: The effects of maternal cigarette smoking on the second trimester human fetal ovary, fetal endocrine signalling and fetal chemical burden were studied. A total of 105 fetuses were studied, 56 from mothers who smoked during pregnancy and 49 from those who did not.
PARTICIPANTS/MATERIALS, SETTING METHODS: Ovary, liver and plasma samples were collected from electively terminated, normally progressing, second trimester human fetuses. Circulating fetal hormones, levels of 73 fetal ovarian transcripts, protein localization, density of oocytes/primordial follicles and levels of 16 polycyclic aromatic hydrocarbons (PAHs) in the fetal liver were determined.
Circulating fetal estrogen levels were very high and were increased by maternal smoking (ANOVA, P = 0.055-0.004 versus control). Smoke exposure also dysregulated (two-way ANOVA, smoking versus gestation weeks interaction, P = 0.046-0.023) four fetal ovarian genes (cytochrome P450 scc [CYP11A1], NOBOX oogenesis homeobox [NOBOX], activator of apoptosis harakiri [HRK], nuclear receptor subfamily 2, group E, member 1 [NR2E1]), shifted the ovarian Inhibin βA/inhibin α ratio (NHBA/INHA) transcript ratio in favour of activin (ANOVA, P = 0.049 versus control) and reduced the proportion of dominant-negative estrogen receptor 2 (ERβ: ESR2) isoforms in half the exposed fetuses. PAHs, ligands for the aryl hydrocarbon receptor (AHR), were increased nearly 6-fold by maternal smoking (ANOVA, P = 0.011 versus control). A fifth transcript, COUP transcription factor 1 (nuclear receptor subfamily 2, group F, member 1: NR2F1, which contains multiple AHR-binding sites), was both significantly increased (ANOVA, P = 0.026 versus control) and dysregulated by (two-way ANOVA, smoking versus gestation weeks interaction, P = 0.021) maternal smoking. NR2F1 is associated with repression of FSHR expression and smoke-exposed ovaries failed to show the normal increase in FSHR expression during the second trimester. There was a significantly higher number of DEAD (Asp-Glu-Ala-Asp) box polypeptide 4 (DDX4) VASA-positive (ANOVA, P = 0.016 versus control), but not POU domain, class 1, transcription factor 1 (POU5F1) OCT3/4-positive, oocytes in smoke-exposed fetuses and this matched with a significantly higher number of primordial follicles (ANOVA, P = 0.024 versus control).
LIMITATIONS, REASONS FOR CAUTION: The effects of maternal smoking on establishment of the maximum fetal primordial follicle pool cannot be reliably studied in our population since the process is not completed until 28 weeks of gestation and normal fetuses older than 21 weeks of gestation are not available for study. Our data suggest that some fetal ovaries are affected by smoke exposure while others are not, indicating that additional studies, with larger numbers, may show more significant effects.
Fetal exposure to chemicals in cigarette smoke is known to lead to reduced fecundity in women. Our study suggests, for the first time, that this occurs via mechanisms involving activation of AHR, disruption of inhibin/activin and estrogen signalling, increased exposure to estrogen and dysregulation of multiple molecular pathways in the exposed human fetal ovary. Our data also suggest that alterations in the ESR2 positive and dominant negative isoforms may be associated with reduced sensitivity of some fetuses to increased estrogens and maternal smoking.
STUDY FUNDING/COMPETING INTEREST(S): The study was supported by grants from the Chief Scientist Office (Scottish Executive, CZG/1/109, and CZG/4/742), NHS Grampian Endowments (08/02), the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 212885, a Society for Reproduction & Fertility summer studentship, Medical Research Scotland (research grant 354 FRG) and the Medical Research Council (WBS: U.1276.00.002.00001 and G1100357). The authors declare they have no competing interests, be it financial, personal or professional.
母亲吸烟如何扰乱人类胎儿卵巢的发育？
母亲吸烟会增加胎儿的雌激素水平，并扰乱胎儿卵巢的几个发育过程。
怀孕期间接触母体吸烟会减少人类胎儿卵巢细胞数量、生殖细胞增殖以及随后的成年生育能力。
研究设计、规模、持续时间：研究了母体吸烟对妊娠中期人类胎儿卵巢、胎儿内分泌信号和胎儿化学负荷的影响。共研究了 105 例胎儿，其中 56 例来自吸烟的母亲，49 例来自不吸烟的母亲。
参与者/材料、设置方法：从选择性终止、正常进展的妊娠中期人类胎儿中收集卵巢、肝脏和血浆样本。测定循环胎儿激素、73 个胎儿卵巢转录本的水平、蛋白质定位、卵母细胞/原始卵泡的密度以及胎儿肝脏中 16 种多环芳烃（PAHs）的水平。
循环胎儿雌激素水平非常高，并因母亲吸烟而增加（方差分析，P=0.055-0.004 与对照相比）。暴露于烟雾还会扰乱（双向方差分析，吸烟与妊娠周数的相互作用，P=0.046-0.023）四个胎儿卵巢基因（细胞色素 P450 scc [CYP11A1]、NOBOX 卵母细胞同源盒 [NOBOX]、凋亡激活因子 harakiri [HRK]、核受体亚家族 2，E 组，成员 1 [NR2E1]），有利于激活素的卵巢抑制素βA/抑制素α 比值（NHBA/INHA）转录比值（方差分析，P=0.049 与对照相比），并使暴露胎儿中一半的雌激素受体 2（ERβ：ESR2）的显性负性异构体减少一半。多环芳烃（AHR 的配体）因母亲吸烟而增加近 6 倍（方差分析，P=0.011 与对照相比）。第五个转录本，COUP 转录因子 1（核受体亚家族 2，F 组，成员 1：NR2F1，其包含多个 AHR 结合位点），无论是显著增加（方差分析，P=0.026 与对照相比）还是受（双向方差分析，吸烟与妊娠周数的相互作用，P=0.021）母亲吸烟的干扰。NR2F1 与抑制 FSHR 表达有关，暴露于烟雾的卵巢在妊娠中期未能表现出 FSHR 表达的正常增加。在烟雾暴露的胎儿中，DEAD（Asp-Glu-Ala-Asp）框多肽 4（DDX4）VASA 阳性的卵母细胞数量明显增加（方差分析，P=0.016 与对照相比），但 POU 域，类 1，转录因子 1（POU5F1）OCT3/4 阳性的卵母细胞没有增加（方差分析，P=0.024 与对照相比）。
局限性、谨慎的原因：由于该过程要到 28 周妊娠才能完成，而 21 周以上的正常胎儿无法用于研究，因此我们无法可靠地研究母体吸烟对建立最大胎儿原始卵泡库的影响。我们的数据表明，一些胎儿卵巢受到烟雾暴露的影响，而另一些则没有，这表明更大规模的额外研究可能会显示出更显著的影响。
已知胎儿暴露于香烟烟雾中的化学物质会导致女性生育能力下降。我们的研究首次表明，这是通过激活 AHR、破坏抑制素/激活素和雌激素信号、增加雌激素暴露以及扰乱暴露于人类胎儿卵巢的多个分子途径来实现的。我们的数据还表明，ESR2 阳性和显性负性异构体的改变可能与一些胎儿对增加的雌激素和母体吸烟的敏感性降低有关。
研究资金/竞争利益：该研究得到了苏格兰首席科学家办公室（苏格兰行政院，CZG/1/109 和 CZG/4/742）、NHS 格雷姆潘恩德（08/02）、欧盟第七框架计划（FP7/2007-2013）的赠款（第 212885 号协议）、生殖与生育学会暑期学生奖学金、苏格兰医学研究协会（研究赠款 354 FRG）和医学研究理事会（WBS：U.1276.00.002.00001 和 G1100357）的支持。作者声明他们没有任何竞争利益，无论是财务、个人还是专业利益。
